Land based sources of pollution//source estimates

[Bob Buddemeier]

Alina et al. --

1.  Conrad and Ian covered most of the basic points, but I think that what is
potentially a new twist is considering the role of the build up of specifically
terrigenous sediment (more fines) as a regional, as well as a local lagoon-specific
phenomenon.
2.  Your wind comments fit will with my memory of encountering the increased wave
height findings somewhere -- alas, location forgotten.  There are a lot of climate
and ocean data available if one pokes around the web...
3.  My callous pragmatism says that if all of the factors are operating against a
reef, the manager should flick it in and find something that promises to respond
better to management -- and that's especially true if any of the stresses are
long-term endogenous factors, as existing sediment load could turn out to be. If we
try to save everything we may wind up saving nothing, especially in few of the
apparently inevitable increase in some of the stress factors (committed warming and
CO2 effects).

It seems obvious from the exchanges that a lot of us have ideas and observations we
never got around to publishing -- maybe the question is how we turn the discussion
thread into a minireview of some sort (?).

Bob

"Alina M. Szmant" wrote:

> Bob and others:
>
> Conrad Neumann and Ian MacIntyre published  the phrase years ago about
> coral reefs being "shot in the back by their own lagoons" Proc 5th Internat
> Coral Reef Congr, Tahiti 1985:  vol 3 pg 105-110), which is the Holocene
> sea level scenario you described in your email.  I agree that for some
> areas (such as Florida Keys) resuspended sediment is a major factor
> limiting coral recruitment (especially sand-blasting by coarse sediments
> during winter storms) and this may have been happening for decades if not
> longer and thus be one reason why patch reefs in Fl Keys often have higher
> coral cover and diversity than more offshore (exposed) reefs inspite of the
> lower water quality (turbidity etc) closer to shore (see Miller et all,
> Coral Reefs vol 19 (2)).  I am always amazed at the high numbers of coral
> recruits we see on these inshore patch reefs ins spite of what the text
> books tell us are unfavorable conditions.  However, bioerosion is likely
> higher inshore and not many of these patch reefs amount to much.
>
> I have a hypothesis that I have been bandying around for a few years that
> it's been more windy since the mid 1980s and 1990s which could be an effect
> of global warming (more heat, more wind) [this is based on a gut impression
> that in spite of having bigger and better boats than I had access to in the
> 1970's, we have more days that we are weathered out now than a few decades
> back].   More frequent or more severe storms all year long could result in
> lower overall water clarity in areas like the Florida Keys where there is
> lots of sediment to resuspend (I gave a presentation about all this in
> Bali, but mea culpa, mea culpa I haven't written it up yet).  If those of
> you that like to work with climate data would have access to good wind
> records, I suggest someone look at the frequency and duration of higher
> wind events over the past 50 years or more, by passing the data thru some
> kind of filter that looks for the higerh energy events (e.g. 15+ knots for
> 24+ hrs):  it takes a minimum period of high winds to really get things
> stirred up, but if the rough conditions persist for too long, suspended
> sediments are likely flushed out of the system).  Thus, not enough
> resuspension could result in fine sediments building up to eventually
> become a problem (nutrients will also build up); frequent moderate energy
> events may make the system turbid a lot of the time depending on whether
> net flow rids the system of the resuspended fines; occasional major events
> help flush the system of both sediments and nutrients.  Thus wind regimes
> (and their change over time as climate changes) could make a big difference
> in the environment conditions reefs have to deal with, and their "health".
>
> Again, things are much more complicated than one-factor causality, and the
> various factors work at different time and spatial scales.  Effects of
> elevated temperatures and over-fishing strike pretty much everywhere which
> is why I think they are at the top of my list of what needs to be addressed
> by managers; sediments and nutrients are very important in some areas and
> not others, and should be addressed where appropriate.  Some poor reef
> areas have all of the above impacting them and that is real sad.  I agree
> with those that write that we shouldn't try to make our favorite cause of
> decline be accepted by everyone as THE ONE to be concerned about, but I
> think we do need a scientifically founded way to attribute relative effects
> because whether we like it or not, that is what the managers need.
>
> Alina Szmant
>
> At 06:57 AM 10/03/2001 -0500, Bob Buddemeier wrote:
> >List --
> >
> >Comment first, then some more discussion of (mostly sediment-related) issues.
> >
> >Special thanks to Katharina and Alina for their observations and comments.
> >Katharina is right on with her comments on single variable arguments --
> >the problem
> >is, we have to understand the variables one by one to get to the point of
> >effective
> >integration, and that seems to tempt a lot of people into the
> >all-or-nothing false
> >dichotomy.  Another problem is the gravitation toward polar positions:
> >"reefs are
> >doomed real soon because people are killing them off" vs "not too worry,
> >they're
> >robust and it's just a natural fluctuation."  The first is a very slightly
> >more
> >credible position than the second, I think, but only slightly, and the
> >most useful
> >synthesis combines and is offset from that discussional axis.
> >
> >Turbidity and sediment are good examples.  Without claiming that they are
> >totally
> >generalizable, let's take the recent contributions to the discussion to
> >show that
> >resuspension of sediment (as opposed to new input) is a significant stress
> >factor.
> >I suggest that this is at least partly a 'natural cycle'
> >development.  Continental
> >shelves and shallow coastal areas are excellent sediment traps, retaining
> >a lot of
> >what comes off the land.  Our present situation is geologically and
> >environmentally
> >anomalous -- a relatively stable 3-6,000 year sea level high stand (the
> >range of
> >times is because it's local, not eustatic, level that counts
> >operationally, and the
> >Caribbean and much of the Indo-Pacific have different local sea level
> >histories).
> >That accounts for a lot of sediment build-up (with or without human
> >intervention),
> >and I suggest that a number of areas may 'simply' have reached a critical
> >threshold
> >in terms of the inventory or load of resuspendable sediment.  A glance at the
> >Pleistocene sea level curve will show why corals and reefs are not necessarily
> >adapted to this kind of environment.
> >
> >I put 'simply' in quotes above to underline Katharina's point that it never is
> >simple -- in this case, one of the complicating human factors is change in the
> >ocean climate.  As I understand it, a number of regions of the oceans have
> >shown
> >significant increases in mean wave height over the past few decades.  This
> >is the
> >resuspension driver, so it may be that either natural climate cycling or
> >human-induced climate change have pushed the sediment resuspension effects
> >across
> >the threshold very recently.
> >
> >This underlines a point that I hope was obvious from the earlier
> >discussions --
> >reef researchers need to understand some oceanography, as well as issues of
> >large-scale dynamics (the latter comment is a shameless plug for an upcoming
> >special issue of Coral Reefs -- sorry).
> >
> >It also puts some other perspectives on the questions of reef doom and
> >what to do
> >about it. Note that I am going to talk about a particular variable or suite of
> >variables, and do not intend to imply that there aren't others, that
> >people aren't
> >problems, etc.
> >1.  'Land sources' in the real-time sense may not be as big a sediment
> >issue as
> >often supposed.  Most large and medium -sized drainage basins have had
> >their water
> >flow (for sure) and sediment discharge (proabably but not always) reduced and
> >regulated by damming and diversion.  Local coastal runoff and
> >small/undeveloped
> >basins have the potential for dramatic increases in sediment load in
> >response to
> >land use and cover changes, but the acute effects of these are often
> >localized near
> >shore (although there is the general contribution to shelf sediment load
> >build-up).
> >
> >2.  There is no realistic prospect of modifying either the coastal zone
> >sediment
> >inventory or the marine energy regime, so -- if this formulation is valid --
> >chronic sediment stresses in most offshore areas may be something that
> >simply has
> >to be lived (or died) with.  This implies a focus on understanding its
> >contribution
> >to multi-stress synergism in hopes of finding a different factor that can be
> >managed to reduce the combined system impact.
> >3.  Conservation/preservation:  I have been beating the drum for a triage
> >approach
> >to reef resarch conservation, and management, and I have also from time to
> >time
> >expressed a fondness for atolls (but outer-shelf reefs can be OK too).  I
> >suggest
> >that this example reinforces both -- if continental reefs really have
> >"timed out"
> >in terms of Holocene habitat development, the places to look for healthy or at
> >least preservable systems are in very well-flushed, no-soft-sediment
> >coastal areas
> >or away from terrigenous sediment sources (e.g., ocean islands, especially
> >with
> >small land mass).
> >4.  Research implications:  This point goes beyond the sediment
> >resuspension issue
> >to the larger question of combined (and especially land-derived)
> >threats.  The idea
> >of chronic stress build-up to a threshold transition that we are now observing
> >implies not only that we are not currently working on normal or 'healthy'
> >systems,
> >but also that what we take as our pre-transition baseline was probably
> >seriously
> >affected at the subclinical level.  This means that much of the coral
> >lierature on
> >function and condition has to be interpreted very cautiously if one is
> >interested
> >in determining 'normal' or 'optimal' function.  Jeremy Jackson has made
> >this point
> >with respect to anthropogenic ecosystem alterations; I propose extending
> >it to a
> >broader suite of 'natural cycle' considerations including sediment buildup on
> >shelves, the implications (for accomodation space and circulation, among other
> >factors) of reef 'catch-up' with sea level, etc.
> >
> >All of which may help explain why I am of the opinion that most
> >'reefs-as-we-know-them' are on their way out of the picture, especially if
> >they are
> >closely associated with a major landmass.  I would rather not use 'doomed'
> >as a
> >blanket statement, because I think there may be some (significantly altered)
> >oceanic survivors.  The moral of the story:  Go to sea.
> >
> >Bob Buddemeier
>
> > > ~~~~~~~
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--
Dr. Robert W. Buddemeier
Kansas Geological Survey
University of Kansas
1930 Constant Avenue
Lawrence, KS 66047 USA
Ph (1) (785) 864-2112
Fax (1) (785) 864-5317
e-mail:  buddrw at kgs.ukans.edu


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